Effect of corrosion on fatigue life prediction of high temperature exhaust manifolds

Important results from the project

In this project, LCF is tested in Ar and in exhaust gas. The results show that environment has big influence on fatigue life. For SiMo51 at 700 C, the corrosive gas reduced fatigue life by 30-50% compared with air and by 60-75% compared with an inert environment. The reduced fatigue life was associated with a mechanism whereby the crack tip oxidized, followed by crack growth. Thus another potential benefit of TBC systems is that the bond coat may reduce oxidation interactions and further improve fatigue life. The goals have been fulfilled according to the plan and A Ph.D. degree is achieved.

Expected long term effects

The results can be used for selecting materials for increased exhaust temperature applications. Combining the different approaches of alloy modification, new material testing and improving the performance using coatings widened the scope of how component life in exhaust manifolds can be improved. Moreover, the findings on SiMo51 provide a completely new understanding of corrosion fatigue in ductile irons. The novel facility developed for high-temperature corrosion fatigue testing can be useful to other researchers working in this field.

Approach and implementation

Since it is expensive to run LCF-test externally, it was decided at very beginning that KTH will build up a laboratory for LCF-test in environments and at high temperature. The project contents are therefore clearly listed as following: Build up equipment for LCF-test; LCF-test in Ar and in exhaust environment; Thermal cycle test of different TBCs; Studies of TBCs on manifolds inside-surfaces; Doctors thesis; The steering and project groups have regularly had meetings for check and follow-up of project status, and for ensuring the resources needed to achieve the project deliverables.

External links

Blogg för labbetCorrFat --- Effect of corrosion on fatigue life prediction of high temperature exhaust manifold